The term “noncoordinating anion”(NCA) is now accepted terminology in the field of olefin and vinyl molecule, coordination, insertion, and carbocationic polymerization. See, for example, EP 0 277 003, EP 0 277 004, U.S. Pat. No. 5,198,401, U.S. Pat. No. 5,278,119, and Baird, Michael C., et al, J. Am. Chem. Soc. 1994, 116, 6435-6436. The noncoordinating anions are described to function as electronic stabilizing cocatalysts, or counterions, for essentially active, cationic metallocene polymerization catalysts. The term noncoordinating anion applies both to truly noncoordinating anions and to coordinating anions that are labile enough to undergo replacement by olefinically or acetylenically unsaturated molecules at the insertion site. These noncoordinating anions can be effectively introduced into a polymerization medium as Bronsted acid salts containing charge-balancing countercations, as ionic cocatalyst compounds, or mixed with an organometallic catalyst before adding it to the polymerization medium. See also, the review articles by S. H. Strauss, “The Search for Larger and More Weakly Coordinating Anions,” Chem. Rev., 93, 927-942 (1993).
U.S. Pat. No. 5,502,017, to Marks et al., addresses ionic metallocene polymerization catalysts for olefin polymerization containing a weakly coordinating anion comprising boron substituted with halogenated aryl substituents preferably containing silylalkyl substitution, such as a t-butyldimethyl-silyl substitution. Marks et al. disclose the weakly coordinating anion as the cocatalyst. The silylalkyl substitution is said to increase the solubility and thermal stability of the resulting metallocene salts. Examples 3-5 describe synthesis of and polymerization with the cocatalyst compound triphenylcarbenium tetrakis (4-dimethyl-t-butylsilyl-2, 3, 5, 6-tetrafluorophenyl) borate.
Leon A. Hagelee and Roland Köster published “Boron Compounds XLIV1, The influence of silicon on the formation of (Z/E)-tetrasubstituted ethylenes via 1-alkynylborates; Syn. React. Inorg. Metal-Org. Chem., 7(1), 53-67 (1977). This reference reports on NMR studies of borates that incorporate tri-methyl silyl groups.
Wrackmeyer, et al., published “1,6-Dihydro-1,6-disilapentalene derivatives by 1,1-organoboration of triynes”. The triynes R1C≡—SiMe2—C≡C—SiMe2—C≡CR1[R1═H, SiMe3, SnMe3] were prepared, and their reactivity towards trior-ganoboranes R3B 6 [R═Et (a), CH2Ph (b), Ph c, 2-thienyl (d)] was studied. The products were characterised by their 1H-, 11B-, 13C-, 29Si- and 119Sn-NMR data.
Yamaguchi, et al., published “Tridurylboranes Extended by Three Arylethynyl Groups as a New Family of Boron-Based π-Electron Systems”. A series of tris(phenylethynylduryl)boranes (R—C6H4—C≡C-duryl)3B with various substituents R have been prepared as air-stable solids owing to the steric protection of the boron atom by the three bulky duryl groups. These compounds show unique photophysical properties.
Imamoto, et al., published “Syntheses and Properties of Trifluoromethane-sulfonyloxy Derivatives of Tricyclohexylphosphine-Borane”. Syntheses, structural characterizations, and reactions of tricyclohexylphosphine-trifluoromethanesulfonyloxyborane and tricyclohexylphosphine-bis(trifluoromethanesulfonyloxy)-borane are described.
In view of the above, there is a continuing need for olefin polymerization activators both to improve the industrial economics of solution polymerization and to provide alternative activating compounds for ionic, olefin polymerization catalyst systems.